Zugl.: Berlin, Techn. Univ., Diss., 2009

Techn. University, Diss., 2005--Darmstadt.

[pt] Este trabalho consiste no desenvolvimento de um algoritmo heurístico para alocação de portadora de telefonia FDM/ FM em repetidores não lineares. Os métodos matemáticos existentes e a quantidade de alternativas impendem que um método exaustivo seja empregado. É proposto então, como solução alternativa, um algoritmo sub-ótimo que inicialmente determina as larguras de faixa das portadoras e a seguir as suas fequências centrais de modo a minimizar a potência total de intermodulação. / [en] This work is concerned with the development of an heuristc algorithm for FDM/ FM telephony carrier allocation in nonlinear repeaters. The existing mathematical methods and the amount of possibilities preclude the use on an exhaustive procedure. Therefore a sub-optimal algorithm is proposed as an alternative solution which initially determines the carrier’s bandwidth in order to minimize the total intermodulation power.

The interest in higher data rate systems is rising very quickly in the area of wireless communications. High data rates mean high Peak to Average Ratio, PAR. This imposes big challenge on the linearity requirement of Power Amplifiers, PAs. The simplest technique that has been used is backing off the PA. However, this leads to very inefficient performance. A lot of more complex techniques were suggested in the literatures to trick the tradeoff between linearity and efficiency. So we discuss the advantages and disadvantages of those techniques. In addition we suggest a new technique called Power Amplifier Linearization using a Mirror Predistorter. This technique is based on the use of a mirror PA that generates a copy of the main PA nonlinearity, and then feeds it in the proper phase and magnitude into the input in order to cancel the intermodulation terms at the output. Simulation and on the bench lab results validate the suggested technique. Also a hybrid PA module was designed and tested based on the suggested technique, and showed an improvement of 23 dB in the Third Order Intermodulation to Carrier ratio, IMD3 of the PA at 7.5 dB back off. / Master of Science

A coaxial loudspeaker in which the woofer and tweeter oscillate at angular frequencies ω_1 and ω_2 respectively, is known to produce sum and difference frequencies ω_± = ω_1 ± ω_2. The generation of these can be attributed to both the nonlinearity of the equations of motion and the Lagrangian boundary behaviour of the low-frequency transducer. In order to characterize the phenomena of interest a perturbation expansion of the field variables is introduced (sometimes called quasi-linear approximation). After deriving a second-order equation for pressure, from which the intermodulation frequencies are obtained, an attempt is made to justify the dominance of the boundary mechanism over that of the fluid nonlinearity. An exact integral solution is then given for the spatial factor of the ω_± pressure terms. In the special case of a farfield on-axis observer an analytic solution is obtained. Several numerical investigations are performed and compared with experiment.

A coaxial loudspeaker in which the woofer and tweeter oscillate at angular frequencies ω_1 and ω_2 respectively, is known to produce sum and difference frequencies ω_± = ω_1 ± ω_2. The generation of these can be attributed to both the nonlinearity of the equations of motion and the Lagrangian boundary behaviour of the low-frequency transducer. In order to characterize the phenomena of interest a perturbation expansion of the field variables is introduced (sometimes called quasi-linear approximation). After deriving a second-order equation for pressure, from which the intermodulation frequencies are obtained, an attempt is made to justify the dominance of the boundary mechanism over that of the fluid nonlinearity. An exact integral solution is then given for the spatial factor of the ω_± pressure terms. In the special case of a farfield on-axis observer an analytic solution is obtained. Several numerical investigations are performed and compared with experiment.

Zugl.: Kassel, Univ., Diss., 2008

Techn. Universiẗat, Diss., 2003--Berlin.

Linear and nonlinear microwave properties of chemical vapor deposition (CVD)-grown graphene are characterized by incorporating a coplanar waveguide (CPW) transmission-line test structure. The intrinsic linear transport properties (S-parameters) of the graphene sample are measured and extracted via a deembedding procedure and then fitted with an equivalent circuit model up to 10 GHz. A statistical uncertainty analysis based on multiple measurements is implemented to esti- mate the error of the extracted graphene linear parameters as well. Nonlinear properties (second- and third-order harmonics as a function of fundamental input power) of the sample are also measured with a fundamental input signal of 1 GHz. Clear harmonics generated from graphene are observed, while no obvious fundamental power saturation is seen. The measured nonlinearity is applied in a graphene patch antenna case study to understand its influence on potential applications in terms of third-order intermodulation levels.

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / This paper describes technical problems in system integration, Intermodulatin interference, digitalization, obital accuracy, low-noise design of the new generation TT&C system as well as their solutions.